In handheld portable work apparatus, the tool is driven by an internal combustion engine to which a mixture, which is to be combusted, is supplied by a carburetor. The power output of the internal combustion engine is adjustable via a throttle pull. The throttle pull has a pull wire which is connected to an actuating element which, in most cases, is the throttle flap of the carburetor. The carburetor is fixed to the inlet of the engine with a spacer interposed therebetween in order to make possible a compact contour of the housing of the engine and to counter an unwanted influencing of the temperature of the carburetor by the heat of the engine. The pull wire is guided via an adjusting device in order to adjust the effective length of the pull line and therefore the idle position and full-load position of the carburetor. The adjusting device comprises a pivotably journalled tension piece. The tension piece is journalled with a bolt which is provided with a spring nut for securely holding the same. This assembly movement can be automated only with difficulty and is therefore still carried out manually and therefore is time intensive. Furthermore, it has been shown time and again during the operation of work apparatus, which are equipped with such a throttle pull guide, that a precise adjustment of idle is only possible with a corresponding expenditure of time. The adjusting device is further subjected to considerable vibrations of the engine which ultimately can affect the adjustment of the length of the pull wire.
It is an object of the invention to provide an adjusting device for a throttle pull of an internal combustion engine which is easily assembled.
The adjusting device of the invention is for a throttle pull of an internal combustion engine including an engine of a portable handheld work apparatus. The engine includes a carburetor having an actuating member and the throttle pull includes a pull wire connected to the actuating member. The adjusting device includes: a spacer; the carburetor being connected to the inlet of the engine with the spacer being disposed therebetween; a support; a tension piece having a pivotable arm on which a segment of the pull wire lies and the tension piece holding the segment by being in contact engagement with the support; a bolt for pivotally journalling the tension piece on the spacer; an adjusting screw threadably engaged in the pivot arm for adjusting the position of the tension piece; the adjusting screw being disposed radially of the bolt and being screwable out of the pivot arm in a direction toward the support; the tension piece and the bolt being configured as a single piece; the bolt defining a longitudinal axis; and, means for securely holding the tension piece in the direction of the longitudinal axis.
The adjusting device is provided with a tension piece which is pivotably journalled on the spacer by means of a bolt formed thereon as one piece. A segment of the pull wire lies on the pivotable arm of the tension piece. The pull wire holds the tension piece in contact engagement on a support. The effective length of the pull wire is adjustable with an adjusting screw. The adjusting screw lies at a radial spacing from the bolt and can be screwed axially out of the pivot arm in a direction toward the support.
A common component can be assembled onto the spacer because of the one-piece configuration of the tension piece with the bolt. According to the invention, the common component is held in the axial direction of the bolt by a form-tight connection. In this way, only one component has to be attached to the spacer during assembly and the complex axial attachment which was required previously is unnecessary.
A practical form-tight holding of the tension piece to the spacer is provided by a key which projects radially from the bolt. The bearing eye of the spacer is provided with a through cut or opening which has a cross section corresponding to the key. The key forms a bayonet latch with the bearing eye in the built-in position of the tension piece with an angular offset. The key on the bolt and the through opening on the spacer are provided at such an angular position relative to each other that the bolt can be pushed into the bearing eye in an angular position during assembly of the tension piece and this angular position lies outside of the angular pivot range of the tension piece which can be adjusted with the adjusting screw. The key can then lie approximately perpendicular to the axis of the adjusting screw. For an angular offset of the key relative to the through opening of approximately 10xc2x0 to 120xc2x0 (preferably approximately 90xc2x0), the tension piece can be seated in a position lying far outside of the adjustable angular pivot range and can be brought into the assembled position with a rotation during the assembly of the tension piece. The key engages behind the bearing eye of the spacer and ensures the axial form-tight holding thereof.
Preferably, the tension piece is pivotally movably mounted between the respective mutually adjacent sides of the carburetor and the spacer with axial guide play in the axial direction of the bolt. The carburetor itself can serve also as a single measure for axial form-tightly holding the tension piece. The tension piece is held in every adjustable position and is secured against the vibrations of the engine. On the side facing toward the spacer, the tension piece is guided on a surface which is formed on the spacer in the vicinity of the bearing eye for the bolt. An advantageous guidance on the side of the spacer facing toward the carburetor is advantageously formed by a support channel configured on the spacer in which a support projection is guided. The support projection projects radially from the tension piece. The support projection is preferably arranged on the support side of the tension piece at the elevation of the bolt and lies on the support channel of the spacer when in the assembled condition. The support side of the spacer has the adjusting screw. The support projection has a radial contour curved about the bolt axis so that in every adjustable tension position of the tension piece, a support is provided and, in this way, only reduced shearing forces develop in the bolt. With an adjustment of the tension piece, the support projection rolls on the support channel. In the tensioned condition of the throttle pull, the occurring transverse forces are carried exclusively by the support projection and the bolt is held free of shear forces and therefore only has a guide function for the pivot movement.
In another embodiment of the invention, a guide wall is formed on the support channel and radially overlaps the support projection of the tension piece. The guide wall holds the support projection, and therefore the tension piece, in axial direction. The guide wall and the support projection lie essentially parallel to each other advantageously with guide play in the axial direction of the bolt whereby also an axial guidance is given on the side of the spacer facing toward the carburetor.